The CB-CID found similarities between the Patna and Chennai blasts and has completed several rounds of probe in multiple locations including Bangalore, Patna and Guwahati and questioned suspects.

The possibility of involvement of Indian Mujahideen and absconding terror suspect Abubacker Siddique with the support of certain terror sleeper cells continues to be probed.

The NIA’s arrest of four persons including Hyder Ali alias ‘Black Beauty’ on May 21 in connection with the Patna bombings ahead of Narendra Modi’s rally last year increased hope that they may hold clues to the blasts here as there were similarities between the two bombings.

Police said “probe details” cannot be disclosed now to the media as investigation was at an “important” juncture.

“Be it NIA, central intelligence agencies or police of other States, we are coordinating and taking help whenever needed. We are following definitive leads,” an official said declining to elaborate.

The police has announced a reward of Rs five lakh to any person who passes on information leading to the identification or arrest of the culprits involved in the twin blasts.